1. Field of the Invention
The present invention relates to an imaging apparatus, such as a digital camera and a video camera, using an image pickup element.
2. Description of the Related Art
In the field of an imaging apparatus, such as a digital camera and a video camera, using an image pickup element to form an image, there has recently been a demand for obtaining a more compact camera with a smaller overall size and forming an image with higher quality.
In an imaging apparatus such as a digital camera, for example, a more compact camera having a smaller thickness (being thinner or slimmer) is demanded with importance paid to portability when the camera is carried by a photographer.
There is known a zoom lens barrel employing a retractable structure, which can efficiently contain a zoom lens, for the purpose of further slimming the camera.
On the other hand, a variable-magnification imaging apparatus is proposed in which an image pickup element is moved following to a focus position that is varied during zooming, in order to realize a simpler and more compact mechanism for a zoom lens (see U.S. Pat. No. 5,587,739).
Also, a slim camera (imaging apparatus) is known in which an optical thickness in the direction toward an object (i.e., in the back-and-forth direction) is reduced by using a folded optical system that includes a reflective member to deflect (fold) an optical axis at substantially 90° (see Japanese Patent Laid-Open No. 2004-37967 and U.S. Pat. No. 6,771,432).
Further, a zoom lens is proposed in which an image pickup element is moved in a folded zoom optical system in accordance with the position of an image plane during zooming, to thereby reduce an overall size of the optical system (see Japanese Patent Laid-Open No. 2005-84151 and No. 2006-106071).
In the zoom lens, conditions for moving various optical units including the image pickup element are required to be properly set in order to compensate for a variation of the image plane position caused with zooming while simplifying a mechanism for moving an optical unit which is moved during zooming.
Also, in the folded-type slimmer zoom lens in which the reflective member is disposed in the light path of the optical system to fold the optical axis for reducing the thickness of the imaging apparatus in the back-and-forth direction, the number of required moving mechanisms is increased and the moving mechanisms become complicated and large in size when the image pickup element is moved independently of another optical unit (which includes a lens unit or includes only an optical member having no refractive power).
Further, from the viewpoint of maintaining high optical performance while reducing the thickness of the imaging apparatus in the back-and-forth direction, it is desired to provide the reflective member for folding the optical axis at an appropriate position in the light path of the optical system and to properly set selection of the optical units which are moved during the zooming.